1. Field of the Invention
My present invention is directed to an improved 1-step process for the preparation of overbased calcium sulfonate greases and thickened compositions. The greases and thickened compositions of the present invention are of the heretofore known thixotropic type which comprise, advantageously, a volatile and/or nonvolatile liquid carrier or solvent, such as, for example, Varsol or mineral spirits, or a mineral oil or equivalent oil medium in their production, and oil-soluble calcium sulfonates derived from oil-soluble higher molecular weight sulfonic acids, which greases and thickened compositions also contain calcium carbonate as calcite in colloidal or extremely finely divided form. In accordance with my invention, while such types of greases and thickened compositions have heretofore been prepared by what is known to the art as the 1-step process, such 1-step processes, as heretofore known and practiced, have had various deficiencies which are overcome by my present invention.
2. Background of the Invention and Brief Description of the Prior Art
Thixotropic greases or thickened overbased calcium sulfonate compositions having corrosion-inhibiting properties, and having utility for a variety of uses such as, for instance, in automobile and truck body undercoatings, and for various other purposes, are known to the art and are disclosed in various publications and patents, illustrative of which are U.S. Pat. Nos. 3,242,079; 3,372,115; 3,376,222; 3,377,283; 3,523,898; 3,661,622; 3,671,012; 3,746,643; 3,730,895; 3,816,310, and 3,492,231; and Canadian Pat. No. 949,055. Such greases or thickened compositions have gone into quite widespread use either as such, or admixed with other ingredients to produce compositions for use in a variety of environments, and generally speaking, they are characterized by reasonably good E. P. and antiwear properties, high dropping points, reasonably good resistance to mechanical breakdown, salt spray and water-corrosion resistance, thermal stability at high temperatures, and other desirable properties, as described in the aforesaid patents. Such heretofore known greases or thickened compositions are conventionally prepared by what is known as a 2-step process, as more particularly shown in the aforesaid U.S. Pat. Nos. 3,242,079; 3,372,115; and 3,492,231. They have also been prepared by what is known as a 1-step process, as noted above, and as is shown, for instance, in the aforementioned U.S. Pat. Nos. 3,671,012; 3,746,643; and 3,816,310; and Canadian Pat. No. 949,055, which also disclose heretofore known 2-step processes.
In the 2-step process, as shown particularly in U.S. Pat. Nos. 3,242,079; 3,372,115; and 3,492,231, as referred to above, there is initially prepared, by way of illustration, a Newtonian solution by admixing a normally liquid oil, commonly a mineral oil or a mixture comprising a mineral oil and a non-mineral oil volatile organic solvent, usually a hydrocarbon solvent such as hexane, with a normally liquid sulfonic acid comprising or containing an aliphatic straight or branched chain having at least 12 carbon atoms and preferably having a molecular weight in the range of about 370 to about 700, to which are added calcium oxide and/or calcium hydroxide and with a so-called promoter which serves to produce an overbased calcium sulfonate which commonly may have a metal ratio of at least 4.5, usually substantially higher, and the resulting mixture is heated, under conditions of agitation, and then carbonated. This results in a Newtonian solution containing the overbased calcium sulfonate dissolved or colloidally dispersed in the mineral oil or the like, which solution is then filtered to form a clear solution. The resulting clear Newtonian solution, produced in this first step, is then subjected to treatment by a second step which involves generally vigorous admixing, and usually heating, said first-step produced solution with a so-called converting agent which may, for instance, be water, or water-soluble alcohols or glycol ethers such as methylcellosolve (mono-methyl ether of ethylene glycol), or mixtures of water and such alcohols; or water-soluble acids, such as acetic acid or propionic acid, which second step results in converting the Newtonian solution to a non-Newtonian disperse system in the form of a grease or a thickened composition.
The 1-step process of forming the greases or thickened compositions differs from the 2-step process in that, in the 1-step process, generally speaking, essentially all of the ingredients are mixed together and then carbonated, and there is no separately formed, or separately formed and recovered, Newtonian solution of an overbased calcium sulfonate dissolved or colloidally dispersed in mineral oil or other suitable liquid medium or carrier. From an economic standpoint, the 1-step process has a definite advantage over the 2-step process, but the 1-step process has not gone into commercial use to nearly the extent that has been the case with the 2-step process because the 1-step process, as heretofore known and as heretofore commercially practiced or sought to be practiced, has been characterized by numbers of significant disadvantages.
U.S. Pat. No. 3,746,643 discloses a 1-step process of preparing thixotropic overbased calcium sulfonate greases and rust-inhibiting compositions wherein small amounts of water and an alcohol are incorporated into a mixture of a nonvolatile diluent oil, a calcium carbonate complex, and an oil-soluble calcium sulfonate complex dispersing agent. In said mixture, the calcium sulfonate dispersing agent is stated to range from about 2 to about 65 wt. %; the nonvolatile diluent oil is stated to range from about 5 to 80 wt. %; the calcium carbonate complex is stated to range from about 1 to about 25 wt. %; and the water and alcohol are stated to range from about 1 to about 6 wt. %, and from about 1 to about 40 wt. %, respectively. In addition, the mixture of said ingredients is stated to include, optionally, up to 60 wt. % of a volatile processing solvent. The resulting mixture of ingredients is then stated to be heated under controlled conditions to convert the mixture to a grease or rust-inhibiting composition (when cut back with a light hydrocarbon solvent). The patent points out that, to obtain the desired products, the mixture must be heated to a temperature exceeding 50.degree. C. (122.degree. F.), and that it is necessary in traversing the temperature zone from about 50.degree. C. (122.degree. F.) to about 100.degree. C. (212.degree. F.) that the rate of temperature increase not exceed a certain maximum limit where the amount of water present in the mixture is less than 2.5 moles of water per mole of calcium metal present as the carbonate complex.
U.S. Pat. No. 3,671,012 discloses a 1-step process of preparing thixotropic overbased calcium sulfonate greases and grease-like compositions. This is disclosed more particularly in Column 6, Lines 40 to the bottom of the page, extending through Columns 7 and 8 and through Line 25 in Column 9. The procedure described in U.S. Pat. No. 3,671,012 is generally similar to that shown in U.S. Pat. No. 3,746,643 except that the disclosure in U.S. Pat. No. 3,671,012 is in greater detail than is described in U.S. Pat. No. 3,746,643.
U.S. Pat. No. 3,816,310 is generally similar in its disclosure of known 1-step processes to the 1-step process disclosed in the above referred to U.S. Pat. Nos. 3,746,643 and 3,671,012. Taking as illustrative the 1-step process as described in U.S. Pat. No. 3,816,310, as there described in a typical or illustrative embodiment, an admixture is formed consisting essentially of an oil-soluble sulfonic acid or an oil-soluble calcium sulfonate as a dispersing agent, e.g. linear or branched chain "NAB" Bottoms or a C.sub.15 -C.sub.18 linear alkylbenzene sulfonic acid; liquid medium or carrier material, for instance, a mineral oil; a C.sub.1 -C.sub.3 alkanol, for instance, methyl alcohol; calcium oxide and/or calcium hydroxide; and water; then carbonating the resulting admixture with carbon dioxide while maintaining the temperature below about 165.degree. F. to the extent that at least 1.5 moles of the carbon dioxide per mole of the calcium as calcium carbonate are present in the mixture; and then heating the carbonated admixture to a temperature above 212.degree. F., said heating step being characterized in that the time required to heat to 212.degree. F. is from about 0.5 to about 8 hours, the process being characterized further in that alternatively, the water utilized initially may be added after the carbonation step or just prior to the heating step after the carrying out of the carbonation step. Numbers of nonvolatile liquid media or carrying materials are disclosed, mineral oils generally being preferred where greases are preferred. U.S. Pat. No. 3,816,310 also teaches that a light or relatively volatile hydrocarbon solvent, such as, by way of example, n-decane, benzene, toluene, Stoddard solvent or n-hexane, though not a critical ingredient, may be incorporated into the composition constituting the aforementioned ingredients, and, when included, it is preferable that it be employed in proportions, in terms of wt. %, from about 20 to 80% of the total of the calcium sulfonate and nonvolatile carrier present in the composition to be processed. In those instances in which the final composition produced by the process is to be used as a grease, a high percentage of the mixture of nonvolatile carrier and volatile hydrocarbon solvent should be volatile hydrocarbon solvent; whereas, if the final product produced by the process is to be used as a rust or corrosion protective coating or film, the nonvolatile carrier may be used alone as the carrier or in admixture with relatively smaller amounts of volatile carrier. The patent also specifically states that, when the final product produced by the process of said patent is to be used as a grease, the consistency or thickness of the grease is controlled by using, as the carrier, a relatively nonvolatile mineral oil typically having the general properties of a Bright Stock cut produced in petroleum refining.
U.S. Pat. No. 4,129,589, of which I am one of the joint inventors, discloses a process for preparing overbased oil-soluble magnesium sulfonates having a metal ratio of approximately 10 to approximately 40 by a 1-step process in which oil-soluble magnesium sulfonates dissolved or dispersed in an inert carrier solvent or diluent, such as mineral oils or volatile hydrocarbon solvents such as naphtha, are admixed with a promoter system comprising, for example, acetic acid in admixture with an alcohol such as methanol or an alkoxyalkanol such as methoxy ethanol, and with water; a light magnesium oxide; heating said mixture to from about 50.degree. F. up to the reflux temperature of said mixture; and then carbonating said mixture, after which volatile components may be stripped from the reaction mixture. The resulting overbased, oil-soluble magnesium sulfonates are stated to be useful as additives to lubricants, greases, fuels and the like where they function as detergents and acid neutralizers whereby to reduce wear and corrosion in engines and extending engine life. This patent is irrelevant to my invention because it deals solely with the production of overbased oil-soluble magnesium sulfonates which are Newtonian liquids, which are not thixotropic, and has nothing to do with and contains no suggestion or concept whatever of the preparation of thixotropic overbased calcium sulfonate complexes. The compositions of said patent are worthless and inoperative for the purposes of the thixotropic overbased calcium sulfonate produced in accordance with the 1-step process of my present invention.
One of the main problems with the prior known and practiced 1-step processes for the preparation of thixotropic overbased calcium sulfonate complex greases or thickened products was that of the unpredictability as to whether the greases or thickened products obtained would or would not be at least reasonably satisfactory for commercial usage. Reasonably satisfactory and commercially usable greases and thickened compositions were obtainable, in many instances, in less than 50% of the cases where certain then-known 1-step processes were carried out to produce the desired greases or thickened compositions. Efforts to ascertain why certain batches of greases or thickened compositions were suitable whereas others were not suitable did not lead to any conclusions despite the fact that considerable studies and experimental work were expended in such efforts.